Latest Situation Updates
Mehran Patpour (Global Rust Reference Center in Denmark) and co-authors have just published details of the emergence and spread of virulence to SrTmp in the Ug99 race group in Africa. The note is now available as a First Look in Plant Disease (see http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-06-15-0668-PDN). The report details the results of combined race analysis undertaken by the GRRC, Denmark and the USDA-ARS Cereals Disease Lab, Minnesota on 84 stem rust samples collected in 2014 from Kenya, Uganda, Rwanda and Egypt.
The presence of two new Ug99 race group variants – race TTKTK (Ug99 + virulent on SrTmp) and race TTKTT (Ug99 + virulent on SrTmp and Sr24) were confirmed in Kenya. Race TTKTK was also confirmed in Uganda, Rwanda and Egypt. Detection of these new variants in the Ug99 race group across several countries in a single year indicates the relevance of coordinated surveillance activities and also indicates potentially very rapid geographical dispersal of race TTKTK.
The following is extracted from the BGRI Newsletter Special Edition, 3rd April 2015:
Kenyan Variety Robin Overcome by Two New Ug99 Variants
A popular wheat cultivar, Robin, sustained severe damage in some farmers’ fields by stem rust in the 2014 crop season in Kenya. Robin became popular because of high yield potential and resistance to previously known Ug99 races. The resistance was conferred by stem rust gene SrTmp, which was effective to the previous races of the Ug99 race group. KALRO scientists collected several samples from various field sites, including the stem rust resistance screening nurseries at Njoro, and race analyses conducted by CDL and GRRC identified two new variants in the Ug99 race group, both of which were virulent to SrTmp. One of the two new variants was also detected in the 2014 samples from neighboring countries. The detection of these new races is a result of worldwide efforts in recent years on stem rust surveillance to detect and monitor Ug99 and other significant races that pose a continuous threat to wheat production. During the past years KALRO has released several stem rust resistant wheat varieties and others are at advanced stages of testing in national variety registration trials. Varieties such as ‘Kingbird’, ‘Kenya Tai’, ‘Eagle 10’, ‘Kenya Sunbird’ and ‘Kenya Hawk 10’ continue to be resistant to the new SrTmp virulent variants.
Following the confirmed detection of Ug99 (race TTKSK) in Egypt in 2014 (BGRI special newsletter report April 2015) increased vigilance is needed for stem rust in the eastern Mediterranean. Although no confirmed reports of race TTKSK have been obtained from Egypt in 2015, trace amounts of stem rust (race unknown) were detected in the central delta of Egypt in early March 2015. No further reports of stem rust outbreaks have been reported from Egypt in 2015. Crops in Egypt are now approaching maturity, with harvesting occurring between mid April to mid May. However, if any stem rust inoculum were to build up in Egypt then spore deposition models run jointly by the UK Met Office and Cambridge University indicate that there is a risk of onward movement of spores to the eastern Mediterranean basin. Model results show consistent seasonal deposition patterns over the last 12 years, indicating a higher risk, relative to other areas, of spore deposition for Israel, Lebanon, Jordan, eastern Syria and southern Turkey. During the months April and May typically there is a large spatial variation of deposition patterns, with long-distance dispersal of spores that reach eastern Mediterranean countries (see Fig 1 – Data from March, April, May 2014 used as an illustrative example of typical spore dispersal patterns). The most recent spore deposition forecast maps for the period 8 – 14 April 2015, based on confirmed sites for Ug99 (race TTKSK) in Egypt in 2014 agree well with the long-term dispersal trends. Increased surveillance and monitoring is advised in Israel, Lebanon, Jordan, eastern Syria and southern Turkey. Sampling of any stem rust detected in the eastern Mediterranean and rapid race identity confirmation is recommended (either by race analysis on live samples or through the USDA CDL SNP assay for the Ug99 race group). Please contact Dave Hodson, CIMMYT (email@example.com) for more details on sampling options.